1. Field of the Invention
This invention relates generally to vehicle suspension systems. More particularly, this invention relates to a rear suspension swingarm assembly for supporting a rear wheel of the motorcycle.
2. Description of the Related Art
Motorcycles generally include an engine supported within a cradle-type frame assembly. A typical arrangement includes a front suspension fork assembly supported by the frame for rotation about a steering axis. The fork assembly supports a front wheel of the motorcycle at its lower end. A handlebar assembly is mounted to the suspension fork to permit steering of the front wheel of the motorcycle. An elongated, straddle-type seat assembly is typically supported above the frame. A rear wheel of the motorcycle is commonly supported by a suspension swingarm assembly, which is pivotally supported by, and extends in a rearward direction from, a lower portion of the frame. Thus, both the front and rear wheels are typically suspended for limited, controlled movement along a suspension travel path relative to the frame.
A common swingarm assembly includes a connecting portion, which is typically connected to the motorcycle frame and to which one end of a suspension member, such as a hydraulic shock absorber, is mounted. One or more tubular arms typically extend in a rearward direction from the connecting portion. A rear wheel of the motorcycle is often supported at a rearward end of the arm(s).
In a common arrangement, a hub assembly of the rear wheel is rotatably supported on a shaft, or axle, which is carried by the swingarm assembly. An intermediate member, such as a washer, for example, may be positioned between the hub and an inner surface of the swingarm assembly. A nut is often threaded on one end of the axle and tightened to secure the hub on the axle and to press the hub (and washer, if provided) firmly against the inner surface of the swingarm.
However, vibrations transmitted from the engine, along with forces imparted on the rear wheel when traversing rough terrain, nonetheless result in a slight amount of relative movement between the hub, or washer, and the swingarm. The friction produced from this relative movement tends to wear the inner surface of the swingarm assembly. Over time, such wear may compromise the strength or stiffness of the swingarm assembly. Accordingly, this region of the swingarm assembly may be enlarged to compensate for the impending wear. The size increase, however, disadvantageously adds weight to the assembly.